The present invention relates generally to shoe insoles, and more particularly, to improved insoles particularly adapted for arthritic and/or diabetic people.
In the United States, 42.7 million people are affected by arthritis. This number is expected to grow to 60 million people in the year 2020. Arthritis is the leading cause of disability among people ages 15 or older.
Due to rheumatoid inflammation, all lower extremity joints and the back can experience pain, fatigue and discomfort. Arthritic people commonly experience forefoot pain and swelling in the metatarsal area. This results from a remodeling of the foot, that is, a structural change in the forefoot. Specifically, depressed or prominent metatarsal heads are formed, which result in bony protuberances, and thereby pressure points, at the bottom of the foot, which can be very painful. This, of course, causes impaired ambulatory ability and gait. Further, deformation of foot joints in arthritic people can produce excessive plantar pressure, which will worsen the pain and discomfort in the foot. Arthritic people also experience mid-foot/arch problems.
It has been suggested by Kendon J. Conrad et al, xe2x80x9cImpacts of Foot Orthoses on Pain and Disability in Rheumatoid Arthriticsxe2x80x9d, J. Clin. Epidemiol., Vol. 49, No. 1, pages 1-7, 1996, to use functional posted foot orthoses to provide symptomatic relief of pain in arthritic people. However, Conrad et al concluded from randomized clinical trials that functional posted foot orthoses provide little, if any, benefit over placebo foot orthoses in limiting disability or pain. There as also no indication as to how the foot orthoses were posted. The article does state that the results are contrary to previous tests and beliefs.
In a later article by Meredith B. Marks et al in The Lancet, there is a discussion of the Conrad et al findings. It is stated therein that foot orthoses are commonly used in the management of patients with rheumatoid arthritis who commonly complain of foot pain and deformity due to the combined effects of inflammation, bony destruction and connective tissue damage. Marks et al state that Conrad et al used a corrective wedge as the functional posted foot orthoses, which was made from a rigid thermoplastic material. It was stated that the posting was performed on the basis of a clinical assessment made by a podiatrist, with the aim of limiting pronation by maintaining the subtalar joint in a neutral position at mid-stance, thereby limiting stresses on the forefoot that promote hallux valgus deformities. It was also stated that there is no indication as to how such correction was provided to achieve this positioning. It was, however, further stated that metatarsal relief, in the form of a pad or bar proximal to the metatarsal joints, was not incorporated into the orthoses. It was acknowledged that the Conrad et al study was the first study in a double-blind randomized manner. Marks et al indicate, as well, that the Conrad et al finding is contrary to findings of previous uncontrolled trials and to prevailing beliefs about good clinical practice. Marks et al suggest that more effective pain relief might have been provided by orthoses made from a material with more shock-absorbing properties than Rohadur used in the Conrad et al tests, and including metatarsal relief.
It is also estimated that there are 15.7 million diabetic people in the United States. Because of the deterioration of the soft tissue and neuropathy, diabetic people tend to experience high pressure on the bottom of their feet, especially under the ball of the foot. This high pressure forms high local pressure spots in the forefoot, causing plantar ulceration, and ultimately may result in amputation when patients lose the protective sensation. In fact, this makes diabetes the leading cause of lower extremity amputations. This is because the tissue in the forefoot is sensitive to shear, that is, twisting and torsion, and excessive shear causes the foot ulcers. Therefore, it is important that the shear in the forefoot be absorbed to avoid this problem.
Accordingly, it is an object of the present invention to provide an insole that overcomes the problems with the aforementioned prior art.
It is another object of the present invention to provide an insole particularly suited for diabetic and arthritic people.
It is still another object of the present invention to provide an insole which reduces lower extremity, back and foot pain.
It is yet another object of the present invention to provide an insole which optimally accommodates deformation of the forefoot region and reduces foot plantar pressure in the forefoot region.
It is a further object of the present invention to provide an insole which substantially reduces peak pressure in the midfoot and heel regions.
It is a still further object of the present invention to provide an insole which provides extra stabilization and support in the midfoot arch area.
It is a yet further object of the present invention to provide an insole that is easy and economical to make and use.
In accordance with an aspect of the present invention, a removable insole for insertion into footwear, includes a forefoot portion extending at least to metatarsals of a foot, the forefoot portion including a combination layer formed from a first layer of a resilient material which provides a shock absorption cushioning function, and a second layer of a slow recovery material which absorbs shear forces applied to the second layer at pressure points and spreads out the shear forces along the forefoot portion, the second layer having substantially the same outer dimensions as the first layer and superposed therewith; a heel portion; and a mid-foot portion connecting together the forefoot portion and the heel portion, the mid-foot portion including a medial arch portion.
Preferably, the first layer is the bottom layer and the second layer is the top layer superposed on the bottom layer. A rear edge of the combination layer is connected with a front edge of the mid-foot portion, and the connection occurs at the medial arch portion. Each of the first and second layers has a substantially identical thickness. Unlike the forefoot portion, the mid-foot portion and heel portion are formed by a unitary layer of resilient material.
A top cover is also secured to upper surfaces of the forefoot portion, mid-foot portion and heel portion.
Also, at least one pattern trim line is formed at the forefoot portion for trimming the insole to fit into smaller-size footwear.
The medial arch portion has a height greater than a remainder of the mid-foot portion, and includes spaced apart, transverse oriented grooves at the underside defining transverse flex members therebetween which effectively function as springs.
The heel portion includes a plurality of depressions at the underside which form spaced apart spring walls therebetween, the spring walls having lower edges generally coplanar with a lower surface of the heel portion.
Preferably, the heel portion is cupped so as to be formed by a relatively flat central portion and a sloped side wall. The sloped side wall extends around a periphery of the heel portion and forwardly to at least the mid-foot portion of the insole.
In accordance with another aspect of the present invention, footwear includes an outer sole; an inner sole connected to the outer sole, the inner sole including a forefoot portion extending at least to metatarsals of a foot, the forefoot portion including a combination layer formed from a first layer of a resilient material which provides a shock absorption cushioning function, and a second layer of a slow recovery material which absorbs shear forces applied to the second layer at pressure points and spreads out the shear forces along the forefoot portion, the second layer having substantially the same outer dimensions as the first layer and superposed therewith, a heel portion, and a mid-foot portion connecting together the forefoot portion and the heel portion, the mid-foot portion including a medial arch portion; and an upper connected to at least one of the outer sole and the inner sole.
The above and other features of the invention will become readily apparent from the following detailed description thereof which is to be read in connection with the accompanying drawings.